Evaporator for refrigerating machine and refrigeration apparatus

ABSTRACT

An evaporator for a refrigerating system which prevents droplets of refrigerant from blowing upwards, and a refrigeration apparatus using thereof are provided. The evaporator for a refrigerating system includes a container into which the refrigerant is introduced, and heat exchanger tubes disposed in the container through which a cooled object flows. The evaporator further includes a prevention plate disposed above the heat exchanger tubes so that droplets of the refrigerant, which are blown upwards due to a boiling of the refrigerant, hit the prevention plate.

TECHNICAL FIELD

The present invention relates to an evaporator for a refrigeratingsystem which refrigerates an object to be cooled (e.g., water, brine,etc.) by exchanging heat between the object and the refrigerant, and arefrigeration apparatus using the evaporator.

BACKGROUND ART

In a structure of large scale, such as a tall building, cool water,which has been chilled by a refrigerating system, is circulated througha pipe arrangement disposed in the structure so that heat is exchangedbetween the cool water circulating in the pipe arrangement and airpresent in the spaces of the structure to decrease the temperature ofthe spaces.

FIG. 8 is a diagram showing an example of a conventional evaporatorwhich may be provided with a refrigerator. In this evaporator, aplurality of bundles of heat exchanger tubes 2 through which waterpasses is disposed in a staggered form in a cylindrical container 1 intowhich a refrigerant is introduced.

The plurality of heat exchanger tubes 2 may be divided into two groups,namely, a group of entering tubes which communicate with a waterentrance 3 and a group of exiting tubes which communicate with a waterexit 4. Water enters from the water entrance 3, passes through heatexchanger tubes 2 of the entering tube group in the container 1 to reacha water chamber (not shown in the figure), and then passes through theheat exchanger tubes 2 of the exiting tube group to exit from the waterexit 4. During this process, water is cooled down by heat exchange withthe refrigerant introduced into the container 1, and the refrigerantwhich received heat from the water, in turn, boils and vaporizes.

The vaporized refrigerant is then compressed in a compressor, which isnot shown in the figure, and transferred to a condenser.

In the above-mentioned type of evaporator, however, when the refrigerantis boiled around the heat exchanger tubes 2 and vapor is generated,droplets of the refrigerant are often blown upwards by the force of therefrigerant vapor. Then, some of these droplets of refrigerant aresometimes drawn into the above-mentioned compressor and cause problems,such as a decrease in the performance of the compressor or damage to animpeller.

Although attempts have been made to create open passages (i.e., spacesamong heat exchanger tubes) along the bundle of the heat exchanger tubesin an up-and-down direction as pathways for bubbles generated when therefrigerant boils, the force of the refrigerant vapor blown upwards fromthe opening of the passages is increased in this case.

Accordingly, one of the objects of the present invention is to providean evaporator for a refrigerating system, which is capable of preventingblown upwards of droplets of the refrigerant, and a refrigerationapparatus using the evaporator.

DISCLOSURE OF INVENTION

The present invention provides an evaporator for a refrigerating systemincluding a container into which a refrigerant is introduced, and heatexchanger tubes disposed in the container through which an object to becooled down flows, comprising: a prevention plate disposed above theheat exchanger tubes so that droplets of the refrigerant, which areblown upwards due to boiling of the refrigerant, hit the preventionplate and are prevented from proceeding beyond the prevention plate.

In accordance with another aspect of the invention, the heat exchangertubes are divided into a plurality of vertically spaced groups so that aspace is formed between the groups of the heat exchanger tubes invertical direction; and the prevention plate is disposed above thespace.

In yet another aspect of the invention, the distance between theprevention plate and the heat exchanger tubes at an uppermost level isabout 0.5 to 2 times the diameter of a heat exchanger tube which islocated at the uppermost level.

In yet another aspect of the invention, the prevention plate has a crosssection shaped like an inverted letter “V”, “U”, “W”, etc., and theangle of the prevention plate is designed to be between about 60° and120°.

In yet another aspect of the invention, an end portion of the preventionplate covers at least a part, preferably, half or all, of a heatexchanger tube which is located at the uppermost level of the heatexchanger tubes and is adjacent to the prevention plate.

In yet another aspect of the invention, a group of the heat exchangertubes facing an inner surface of the container is disposed so that aspace is formed between the group of the heat exchanger tubes and thecontainer along the inner surface of the container; and a preventionplate is disposed above the space.

The present invention also provides a refrigeration apparatus,comprising: a compressor for compressing a refrigerant; a condenser forcondensing and liquefying the refrigerant which is compressed in thecompressor; a throttling mechanism for reducing the pressure of theliquefied refrigerant; and an evaporator for cooling down an object tobe cooled by exchanging heat between the object to be cooled and aresultant condensed and pressure-reduced liquefied refrigerant, andevaporating and vaporizing the liquefied refrigerant, wherein theevaporator is one of the above-mentioned evaporators.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a schematic structure of a refrigeratingsystem to which an evaporator according to an embodiment of the presentinvention may be applied.

FIG. 2 is a diagram showing a cross-sectional view of the refrigeratingsystem shown in FIG. 1 cut along the II—II line.

FIG. 3 is a diagram showing a partial enlarged cross-sectional view ofthe arrangement of a prevention plate having a cross sectionsubstantially shaped as an inverted letter “V”.

FIG. 4 is a diagram showing a partial enlarged cross-sectional view ofthe arrangement of a flat prevention plate.

FIG. 5 is a diagram showing a partial enlarged cross-sectional view ofthe arrangement of a plurality of the prevention plates.

FIG. 6 is a perspective view to explain the structure and constructionof an evaporator in a refrigeration apparatus according to an embodimentof the present invention.

FIG. 7 is a schematic piping diagram to explain the configuration of theevaporator in the refrigeration apparatus according to an embodiment ofthe present invention.

FIG. 8 is a diagram showing an example of a conventional evaporatorwhich may be provided with a refrigerator.

BEST MODE FOR CARRYING OUT THE INVENTION

The evaporator for a refrigerating system according to embodiments ofthe present invention will be described with reference to theaccompanying drawings.

FIG. 1 is a diagram showing a schematic structure of a refrigeratingsystem according to an embodiment of the present invention. Therefrigerating system includes a condenser 10, an expansion valve(throttle valve) 11, an evaporator 12, and a compressor 13. Thecondenser 10 condenses and liquefies a refrigerant by exchanging heatbetween cooling water (the cooled object) and the refrigerant which maybe in a vapor phase. The expansion valve 11 decreases the pressure ofthe condensed refrigerant. The evaporator 12 refrigerates the coolingwater by exchanging heat between the cooling water and the condensedrefrigerant. The compressor 13 compresses the refrigerant, which hasbeen evaporated and vaporized in the evaporator 12, and supplies it tothe above-mentioned condenser 10. The cooling water refrigerated in theevaporator 12 may be utilized, for instance, for air-conditioning in abuilding.

FIG. 2 is a diagram showing a cross-sectional view of the refrigeratingsystem shown in FIG. 1 cut along the II—II line indicated by arrows. Asshown in FIG. 2, the evaporator 12 includes a cylindrical container 14into which a refrigerant is introduced, and a plurality of bundles ofheat exchanger tubes 15 disposed in the container 14.

The plurality of heat exchanger tubes 15 is disposed in the longitudinaldirection (i.e., a vertical direction with respect to the sheet surfaceof FIG. 2) of the container 14 and function as pathways for coolingwater, which is the cooled object. The heat exchanger tubes 15 aredivided into groups, namely, a group of entering tubes which communicatewith a cooling water entrance 16 a and a group of exiting tubes whichcommunicate with a cooling water exit 16 b shown in FIG. 1. Thedirection of the flow of cooling water in the heat exchanger tubes 15communicating with the cooling water entrance 16 a is different from thedirection of the flow of cooling water in the heat exchanger tubes 15communicating with the cooling water exit 16 b.

The plurality of heat exchanger tubes 15 may be divided into a pluralityof groups, for instance, four, (i.e., groups of tubes A-D as shown inFIG. 2) in the lower half of the container 14. A space 17 is formedbetween each of the groups A-D of the heat exchanger tubes 15 in avertical direction, and a space 18 is formed between the group A and thecontainer 14 along the inner surface of the container 14, and betweenthe group D and the container 14 along the inner surface of thecontainer 14. Note that the above-mentioned spaces 17 and 18 arehereinafter referred to as passages 17 and 18 since it may be regardedthat they are formed by extracting the corresponding heat exchangertubes 15 which may be present there originally.

A prevention plate 19 having an inverted “V” cross sectional shape isdisposed above each of the passage 17. Also, a blow-up prevention plate20, which may have a flat shape, is disposed above each of the passage18. The shape of the prevention plates 19 and 20 is not particularlylimited, and any suitable shape, such as inverted “U” and “W”, can beused.

As shown in the enlarged view of FIG. 3, the vertical angle θ of theprevention plate 19 in this embodiment is designed to be between about60° and 120°. The prevention plate 19 is disposed at a position abovethe passage 17 so that the right and left portions, respectively, of theprevention plate 19 cover at least a part, preferably, half or all, ofthe corresponding adjacent heat exchanger tube 15 at the uppermostlevel, and that the distance between the right and left edge portions,respectively, of the prevention plate 19 and the corresponding heatexchanger tube 15 be 0.5 to 2 times the diameter D of the heat exchangertube 15.

On the other hand, as shown in the enlarged view of FIG. 4, theprevention plate 20 is disposed above the heat exchanger tube 15 so thatthe edge portion thereof covers at least a part of the correspondingadjacent heat exchanger tube 15 at the uppermost level, and that thedistance between the edge portion of the prevention plate 19 and thecorresponding heat exchanger tube 15 be 0.5 to 2 times the diameter D ofthe heat exchanger tube 15.

Note that although the end portion of the prevention plate 20 isdownwardly bent in order to stop the upward flow from the passage 18 inthe above embodiment, the prevention plate 20 may have a flat shape andno problems would be caused by the use of such a prevention plate 20.

The number of the heat exchanger tubes 15 contained in the groups A-D inthe above embodiment may be chosen to be, for instance, five hundreds.Also, the heat exchanger tubes 15 in each of the groups A-D may bearranged in a staggered manner. That is, the heat exchanger tubes 15 atan upper level are shifted by about half of the distance, i.e., ½offset, between each other in the transverse direction with respect tothe heat exchanger tubes 15 at the next lower level.

In the evaporator 12 having the above-mentioned configuration, therefrigerant is introduced into the container 14 via a lower portionthereof. Since the refrigerant boils when heat is exchanged betweencooling water flowing through the heat exchanger tubes 15 and itself,vapor of the refrigerant is generated around the heat exchanger tubes15, which are mainly located at a lower portion of each of the groupsA-D, and rises to the surface through the passages 17 or 18.

Although the vapor and droplets of refrigerant bubbles up vigorouslyfrom the opening of the passages 17, the ascent rate thereof issignificantly reduced when the vapor and droplets hit theabove-mentioned prevention plates 19 and 20.

As a result, only the vapor of the evaporated refrigerant exits thecontainer 14 via the demister 21. That is, it becomes possible toprevent the droplets of refrigerant from being supplied to thecompressor 13 shown in FIG. 1. Note that the above-mentioned vapor ofthe refrigerant is supplied to the compressor 13 and is compressed.

As mentioned above, according to the evaporator of this embodiment ofthe present invention, since the prevention plates 19 and 20 prevent thedroplets of refrigerant being blown upwards beyond the plates 19 and 20in the container 14, the droplets of refrigerant are not drawn into thecompressor 13. Accordingly, it becomes possible to avoid problems, suchas a decrease in the performance of the compressor or damage to animpeller.

Note that although the prevention plates 19 and 20 are disposed onlyabove the passages 17 and 18 in the above-mentioned embodiments,droplets of refrigerant may sometimes be blown upwards by bubbles of therefrigerant which ascend between the heat exchanger tubes 15 in each ofthe groups A-D. Accordingly, the prevention plates 19 may be disposed soas to cover all of the heat exchanger tubes 15 of the groups A-D asshown in FIG. 5. In this manner, it becomes possible to assuredlyprevent the droplets of refrigerant from entering the compressor 13.

In this embodiment, although each of the prevention plates 19 isdisposed so as to be vertically shifted relative to each other and tooverlap, when viewed from the above, with adjacent prevention plates 19,it is possible to arrange the prevention plates 19 in a differentmanner.

Also, although the passages 17 and 18 are provided in order to decreasethe amount of bubbles in each of the tube groups A-D in the evaporator12 according the above-mentioned embodiments, the present invention,which can prevent the droplets of refrigerant from blowing upwards, mayalso be effectively and suitably applied to an evaporator having nopassages 17 and 18.

The heat exchanger tubes 15 are arranged in the staggered manner in eachof the groups A-D in the above-mentioned embodiments to enhance thecontact between the refrigerant and the heat exchanger tubes 15 and toimprove the heat transfer rate between them.

Next, the overall structure of a refrigeration apparatus including theabove-mentioned evaporator according to an embodiment of the presentinvention will be explained with reference to FIGS. 6 and 7.

The refrigeration apparatus shown in the figures includes theabove-mentioned evaporator 12; a compressor 13 for compressing therefrigerant vaporized in the evaporator 12; a condenser 10 forcondensing and liquefying the refrigerant compressed in the compressor13; an expansion valve (throttle valve) 11 for reducing the pressure ofthe refrigerant liquefied in the condenser 10; an intermediate cooler 25for temporarily storing and cooling the refrigerant liquefied in thecondenser 10; and an oil cooler 26 for cooling the lubricating oil forthe compressor 13 by utilizing a portion of the refrigerant cooled inthe condenser 13.

Also, a motor (a driving mechanism) 27 is connected to the compressor 13for operating the compressor 13.

The condenser 10, the throttle valve 11, the evaporator 12, thecompressor 13, and the intermediate cooler 25 are connected via primarypiping 28 to constitute a closed system in which the refrigerant iscirculated.

The compressor 13 in this embodiment is based on a 2-stage (multistage)centrifugal compressor, a so-called turbo compressor, and this turbocompressor 13 is provided with a plurality of impellers 29. Therefrigerant is compressed in a first stage impeller 29 a situated in theupstream side of the impeller 29, and the compressed refrigerant is ledinto the second stage impeller 29 b to be compressed further and thensent to the condenser 10.

The condenser 10 includes a main condenser 10 a and a sub-cooler 10 bwhich is an auxiliary compressor, and the refrigerant is introducedfirst into the main condenser 10 a and then to the sub-cooler 10 b.However, a portion of the refrigerant cooled in the main condenser 10 ais introduced into the oil cooler 26, without passing through thesub-cooler 10 b, to cool the lubricating oil.

Also, apart from the above process, a portion of the refrigerant cooledin the main condenser 10 a is introduced into the casing 31 of the motor27, which will be explained later, without passing through thesub-cooler 10 b, and cools stators and coils which are not shown in thediagram.

The throttle valve 11 is disposed between the condenser 10 and theintermediate cooler 25, and between the intermediate cooler 25 and theevaporator 12, and they are used for stepwise reduction of the pressureof the refrigerant liquefied in the condenser 10.

The structure of the intermediate cooler 25 is equivalent to a hollowvessel, and the refrigerant which has been cooled in the main condenser10 a and the sub-cooler 10 b and reduced in pressure in the throttlevalve 11, is temporarily stored therein and is subjected to furthercooling. Here, the vapor phase components in the intermediate cooler 25are introduced into the second stage impeller 29 b of the compressor 13through the bypass piping 23, without passing through the evaporator 12.

INDUSTRIAL APPLICABILITY

According to the evaporator of the present invention, since theprevention plates are disposed above the heat exchanger tubes so thatdroplets of refrigerant, which are blown upwards when the refrigerant isboiled, hit the prevention plates, the droplets of refrigerant are notdrawn into the compressor. Accordingly, it becomes possible to avoidproblems caused by the droplets, such as a decrease in the performanceof the compressor or damage to an impeller.

What is claimed is:
 1. An evaporator for a refrigerating systemincluding a container into which a refrigerant is introduced, and heatexchanger tubes disposed in the container through which an object to becooled down flows, comprising: a prevention plate disposed above saidheat exchanger tubes so that droplets of the refrigerant, which areblown upwards due to boiling of the refrigerant, hit said preventionplate.
 2. An evaporator for a refrigerating system according to claim 1,wherein said heat exchanger tubes are divided into a plurality ofvertically spaced groups so that a space is formed between the groups ofsaid heat exchanger tubes in a vertical direction; and said preventionplate is disposed above the space.
 3. An evaporator for a refrigeratingsystem according to claim 1, wherein the distance between saidprevention plate and said heat exchanger tubes at an uppermost level isabout 0.5 to 2 times the diameter of a heat exchanger tube which islocated at the uppermost level.
 4. An evaporator for a refrigeratingsystem according to claim 1, wherein said prevention plate has a crosssection substantially shaped as an inverted letter “V”, and a verticalangle of said prevention plate is designed to be between 60° and 120°.5. An evaporator for a refrigerating system according to claim 1,wherein an end portion of said prevention plate covers at least a partof a heat exchanger tube which is located at the uppermost level of saidheat exchanger tubes and is adjacent to said prevention plate.
 6. Anevaporator for a refrigerating system according to claim 1, wherein agroup of said heat exchanger tubes facing an inner surface of saidcontainer is disposed so that a space is formed between the group ofsaid heat exchanger tubes and said container along the inner surface ofsaid container; and said prevention plate is disposed above said space.7. A refrigeration apparatus, comprising: a compressor for compressing arefrigerant; a condenser for condensing and liquefying the refrigerantwhich is compressed in said compressor; a throttling mechanism for thepressure of the liquefied refrigerant; and an evaporator for coolingdown an object to be cooled by exchanging heat between the object to becooled and a resultant condensed and pressure-reduced liquefiedrefrigerant, and evaporating and vaporizing the liquefied refrigerant,wherein said evaporator comprises: a container into which therefrigerant is introduced; heat exchanger tubes disposed in thecontainer through which the object to be cooled down flows; and aprevention plate disposed above said heat exchanger tubes so thatdroplets of the refrigerant, which are blown upwards due to boiling ofthe refrigerant, hit said prevention plate.
 8. A refrigeration apparatusaccording to claim 7, wherein said heat exchanger tubes are divided intoa plurality of vertically spaced groups so that a space is formedbetween the groups of said heat exchanger tubes in a vertical direction,and said prevention plate is disposed above the space.
 9. Arefrigeration apparatus according to claim 7, wherein the distancebetween said prevention plate and said heat exchanger tubes at anuppermost level is about 0.5 to 2 times the diameter of a heat exchangertube which is located at the uppermost level.
 10. A refrigerationapparatus according to claim 7, wherein said prevention plate has across section substantially shaped as an inverted letter “V”, and avertical angle of said prevention plate is designed to be between 60°and 120°.
 11. A refrigeration apparatus according to claim 7, wherein anend portion of said prevention plate covers at least a part of a heatexchanger tube which is located at the uppermost level of said heatexchanger tubes and is adjacent to said prevention plate.
 12. Arefrigeration apparatus according to claim 7, wherein a group of saidheat exchanger tubes facing an inner surface of said container isdisposed so that a space is formed between the group of said heatexchanger tubes and said container along the inner surface of saidcontainer; and said prevention plate is disposed above said space.